1. Field of the Invention
The present invention relates to a magnetic head for a digital recording and reproducing device such as a flexible disc as an external memory used in a computer.
2. Art Background
FIG. 5 is a perspective view of the assembly of a recording and reproducing core and a pair of erasng cores in a conventional straddle erase type magnetic head for a flexible disc. In FIG. 5, the recording and reproducing core 1 defines a recording and reproducing gap 1a at a predetermined position relative to a side edge 1c of one leg 1b of the core 1. The core 1 is fitted into a narrowed portion 6b of a groove 6 provided in a coupling body of high-melting point glass 3 integral with the erasing cores 2. Cores 2 and coupling body 3 constitutes an erasing core chip 7. The core 1 is secured firmly by a low-melting point glass binder to the core chip 7 so that an erasing gap 2a is provided on each side of the recording and reproducing gap 1a.
The erasing core chip 7 is fabricated as follows. In FIG. 6(a), a recess of a desired shape 5 is cut in a lower surface (as seen in FIG. 6(a)) of a rectangular parallelepiped block of ferrite, sendust or the like 4 which is the material of the erasing core. The recess 5 is then filled with melted high-melting glass material 3. As shown in a perspective view of FIG. 6(b), groove 6 including wide portion 6a and narrower portion 6b is cut in the middle top of block 4 so as to extend into the glass body 3. Both sides of block 4 are then cut into a predetermined shape.
Finally, as shown in a perspective view of FIG. 6(c), block 4 is sliced so as to obtain erasing core chip 7 which includes erasing cores 2 integral with high-melting point glass body 3.
As described above, however, when the erasing core chip 7 including the two erasing cores 2 joined with high-melting point glass body 3 is fitted into and secured firmly to the recording and reproducing core 1, using low-melting point glass as a binder, the narrower groove portion 6b formed in glass body 3 of core chip 7 is eroded and softened by the low-melting point glass, so that the recording and reproducing core 1 is inclined at the narrower groove portion 6b to be deviated from the correct position relative to erasing core chip 7. Thus the erasing gaps 2a become unequal, the gap accuracy, the off-erasing accuracy and the yield of magnetic heads are reduced.